[ Closed ] Filament Extruder - Convert pellets to filament (Page 14 of 58)

Ya that looks way easier to assemble! I like the look of that shaft collar too.  Moving the PID to a side without a flange will give me a bit more vertical clearance to add a bit more height that I need to the enclosure.

With so much bolt sticking out next to the new 8" nipple you probably dont need that rogue screw to keep the hopper upright anymore.

I think its your ears adjusting to the sound.  I cant tell a difference.

Did you use grey ABS pellets or natural with grey masterbatch?

I had the auger cleared out and the nozzle off, so I let it run some pellets cold.  It pushed about 200 pellets out the front in 4 rotations.  If you wanted to mix in some masterbatch with a doser upstream of the hopper, then dropping one pellet into the auger per rotation would give you 50:1.   A better test however would be running pellets through with the hot end taken off so they drop straight from the auger rather than pushed out the front.

I played a little bit with trying to make a filament guide attached to the nozzle, in an effort to have the filament hardened enough before it starts to get sideways stresses.   Getting the hole and the guide lined up is a problem.  I thought maybe rather than a hole drilled through the cap, something like a vented screw could be used instead - http://www.mcmaster.com/#vented-cap-screws/=kyssis 

This could be held onto a cap of some sort at the end of the hot end with nuts and washers.  The end of the nozzle would protrude a bit from the cap and give you something to screw a PTFE tube onto.   You could make your own by drilling a bolt, but that would require a drill press to do properly.  For people without a drill press it might be possible to design a printable jig to guide a hand drill.

Makes sense, thank you for explaining.   I guess I missed that in his PDF.

Ben

That's good data about the auger feed rate! The other good thing to do is calculate the volume of plastic in 200 pellets (weigh them, use density) and compare that to the volume of plastic extruded in 4 rotations, to find out how much the pellets slip along the auger.

The 0.062" vented screws are just about right. It's an interesting idea, using one of those, then tapping some PTFE tube.

I was thinking of getting PTFE round stock, threading it, and tapping a hole in the brass cap, then drilling the whole thing in one go. It's on the list of things to play with, once I get the betas out.

EDIT: Bummer.

Possibly, if the filament gets cool enough from the fan to push through the PTFE. That's the big issue here.

I want to make it clear to everyone that these suggestions are just improvement- the extruder works fine as is, and I've printed a with couple pounds of filament that it's made. We're just trying to make the design more robust and user friendly.

Speaking of which, I let the extruder run for 14 hours last night:

With the motor intentionally misaligned, about 10 degrees, to stress the gearbox. The results:

The motor shaft bearing started wearing, which eventually broke one of the cast pieces of the gearbox plate, where the gear driving the shaft gear sits.

That motor had about 40 hours total runtime on it. I beat on the shaft with a hammer many times, and ran it grossly misaligned. Not bad.

EDIT: Spooled up that filament from the picture above. right at 1kg on the scale, and +/- 0.02mm maximum variation, measured 20 times along the length.

Tim,

So you are seeing about 14 hours for 1kg?

The challenge with the cool zone is that any chance the filament has to catch on something will cause a kink and back up anything behind it.  You can guide the filament across the open space to the guide at the beginning, but if it bends a little, or something happens to create a little extra friction, it will start bending and piling up between the guide and nozzle.  Even a little extra  friction further down will do it too.  I'm trying to figure out a guide because even if it starts out spooling to the floor ok, if I leave it for an extended amount of time I will come back to raman noodles (Makibox must have called theirs ramen because their filament is all squiggly )  I haven't been able to configure the path to the floor in a way that is 100% reliable.

Here is what I am trying for a cool end -

I'm drilling out the cap to 6mm, and tapping it for an M6 bolt.  I'll screw in a M6 hex bolt leaving a few mm sticking out, drill the center with the #52 bit and cut off the hex head.  Then I'll get a PTFE rod, drill and tap one end a short distance to thread onto the bolt and drill something slightly larger than #52 all the way through the center.

The center of the PTFE would be a little larger than the nozzle opening to allow die swell and not require too much pressure to push the plastic through such a long channel.  It should still be narrow and long enough that any movement of the filament at the end will bottom out on the walls before it gets to the nozzle opening.  I picked PTFE because it is slippery, and any pushing of the filament sideways against the walls will hopefully not create enough friction to back up the extrusion.

Drilling into the nozzle from the front and threading the PTFE directly into it is simpler.  However the bottom of the hole will likely be rounded, and the bottom of the tube would be flat.  This would create a small gap between the nozzle opening and the tube,  giving the filament a chance to snag on the edge of the tube.  You could try chamfering the tube to match the rounded profile left by the drill bit, but threading the tube onto an extended bolt seems more foolproof.

Something else I want to try is cutting slots into the PTFE to let air through for cooling.

have you noticed any contamination on your latest batches?

No contamination that I've seen.

The other day, the spool got tangled on the back of the solidoodle, and it cooked the filament for 3 hours. I figured it was a clog for sure, but I hit Extrude and a jet of black goo came out. Printed just fine after that.

I need to run some clear to look for contamination.

I think you guys might be over thinking the cooling aspect of this.  When I have been extruding, the plastic is dam near fully cool by about 4 inches out from the nozzle.  It is usually solid within an inch of leaving the nozzle.  I'm not really sure why you would need these elaborate cooling systems other than the fact that they look cool...

In my case it's not the cooling so much as holding it still so that no movement is allowed within that 1/2" or so when the plastic is soft enough to be deformed.   Increasing cooling to make that zone as short as possible right down to the nozzle opening helps.   An alternative to the coil around the filment might be running that pipe up and down in front of the fan so that the air being blown is colder. 

The problem is also solved by the spooler applying constant tension, but that is of course a lot more complicated.  I hope to have mine built within the next week.  Everything has arrived that needed to be mail ordered, I just need to get the rest of the stuff from the hardware and electronic stores.  Except for the optical sensors- can anyone tell me what I would need to look for?